Injection type mold



Jan. 7, 1941.

|-|.. T. E MSLEY INJECTION TYPE MOLD Filed April 21, 1938 FIG.1.'

2r w 2, Am. 5 @9 6 7 $35 JA H D. L \hlxl 4 m m B, \y m fix T; M

| flwlel f V 1,, v 4N 0 a, 1 m ww r L; 2 a V UA Mm EA 9 I R Q/ Av J 6 Rm B /7 9 Patented Jan. 7, 1 941 UNITED srrlrss PATENT OFFICE 2,227,960"

rivmcrron ma mom Howard T. Emsle'y, Kingsport, Tenn, assignor to EastmanKodak Company, Rochester, N. Y., a

corporation of New Jersey Application April 21, 1938, Serial No. 203,3761 Claim. (Cl. 18-34) This invention relates to injection moldingapcontraction of the mass due to cooling. In this paratus forthermoplastic compositions and more way, an article corresponding to theshape of particularly to an improved injection mold havthe mold can beeasily formed.

ing means for preventing rapid cooling of the The invention will be moreclearly understood 5 thermoplastic composition in the mold gate and byreference to the following detailed descrip- 5 runners. tion andaccompanying drawing, in which:

In the injection molding of thermoplastic ma- Fig. 1 is a sectional viewin elevation of a typiterials, it is customary to maintain the injectioncal injection mold with the dead air chamber mold cold during thecomplete molding cycle, associated with the gate, and

so that-the heated thermoplastic material will Fig. 2 isa plan view ofthe improved mold 10 be quickly cooled. This, of course, cools the takenon the line 22 of Fig. 1. thermoplastic material in the gate and runnersReferring to Fig. 1, there is shown an injecof the mold, as well as thecomposition in the tion mold 5, comprising an upper section 6 and moldcavities in which the molded "article is alower'section I, thehorizontal mold parting line it formed. In general, a relatively smallgate is being at 8. The mold sections are designed to desirable, sincethis reduces the amount'of scrap be moved in a vertical direction towardand away material which is formed on each injection opfrom each other byany suitable means not shown eration and permits more of the compositionto in the drawing. Proper coincidence of the mold go into salableproduction. In order'to form a sections is assured by the engagement ofguide perfect molded article in the cold mold cavity, itpins Ill, whichare mounted in the lower mold 20 is necessary to maintain substantiallythe same section I, with the slots ll positioned in the pressure on thearticle being cooled-as is exerted upper mold section 6. by theinjection plunger on the material in the The mold cavity I2 ispositioned on the partpressure cylinder. However, it has been found ingline of the mold. The molded article is if the gate is of smallcross'section, and the secejected from the mold after the mold is opened2 tion of the molded piece relatively large, the gate by the ejectorpins I3 and M, which are operated tends to freeze first and'thu'sprevent the. transby ejector bar I5, which in turn is actuated bymission of pressure from the'pressu're cylinder rack l6 and gear II. Themold sections conthru the material in the gate to that in the mold, taina plurality of cooling channels l8, through so as well. as preventingadditional material from which a suitable cooling flui such as 0016Water,

flowing into the mold to compensatefor the conis continuously passedduring the molding opertractio'n due to sudden cooling. The mainteation,the connecti P p t be n s ow nance of such pressure during the hardeningis The improved gate structure is mounted in essential to preventshrinkage in the molded, the upper mold section 6 and comprises a gatepiece:; ,Heretofore, increasing the size of the gate bushing l9 having atapering gate 2| passing 35 and-runneraparticularly at the entrance tothe therethrough and Connecting w the runners cavity was about the onlymeans of overcoming 22. The bushing l9 fits tightly in the upper thisdifficulty. n mold section 6 and adjacent its central portion An objectof the present invention is, therethe bushing I9 is grooved at 22,thereby forming fore, an improved m'old construction whereby a dead airspace 23 between the bushing and the 40 cooling of the thermoplasticcomposition in the mold block 6. The relation of the dead air space gateand/or runners is substantially retarded and the cooling chan e is alsoshown in F until after the article in the mold cavity is hard- 2. whichis a p vi w of e sections on the nedp line 2-1 of Fig. 1. It will beevident that the '45 Inaccordance with the invention, this and coolingof the round bushing l9 by the cooling other objects are attained byconstructing the channels l8 will be considerably retarded by the moldwith a dead air chamber around the gate dead air space The mass of theinsulated bushing. The dead air space insulates the gate s e bushing 9 iSuflicient to retain the heat from the cold mold and retards cooling ofthe the'hfllge ong enough to pe the 00111130- material in the gate untilthe composition in the sition to harden in the cooling mold vavities 50mold cavity has hardened into the desired shape. before it hs in e gateand, owin to the Consequently, the injection pressure can b dead airspace insulation, the temperature of the maintained on the compositionbeing cooled in bushing will be maintained at a relatively higher themold cavity and additional composition can temperature than thecorrespon m v y- 65 be forced into the mold to compensate for the WhileI have found that the employment of 2' a dead' air chamber around thegate bushing prevents the thermoplastic composition fromhardening in thegate before it hardens in the cavity, with the result that substantiallythesame pressure can be exerted on the composition in the mold as on thecomposition in the pressure material formed therein. This is aconsiderable saving in material and handling over a given period ofoperation. Furthermore, owing to the soft material in the gate,additional material can be forced into the mold under the operatingpressure to compensate for cooling effects and a well defined moldedarticle can be formed.

What I claim is:

An injection mold for the inJection molding of organic thermoplasticcompositions comprising two halves, one being an ejector hall and theother being a cover half, a mold cavity formed partly in each half, agate within the cover half of the mold for conducting heatedthermoplastic material to the cavity, the walls of said gate,intermediate its ends, being spaced from the cover halt to provide awholly enclosed air space surl0 rounding a substantial portion of thegate, channels within said mold halves adjacent the mold cavity and gatefor conducting cooling fluids to cool the thermoplastic material in themold and gate, said air space being positioned between the gate and theadjacent cooling channels to retard the cooling of the thermoplasticmaterial in the gate without retarding the cooling of the thermoplasticmaterial in the mold cavity.

HOWARD 'r. EMSLEY.

